Several kinds of electrochemical treatments are used for treating industrial and civil exhausts. Among the most common applications, processes producing active chlorine, ozone, peroxides and other active radical species are known, besides electro-oxidative processes for abating microbiological species and for destroying mostly organic species. In the case of aqueous wastes of high organic concentration, electrochemical oxidation treatments are in most of the cases the only alternative to incineration processes, which turn out to be expensive due to the high amount of energy associated with the evaporation of the aqueous fraction and which in any case require a subsequent treatment of gaseous discharges.
There exist, however, wide families of organic species commonly present in industrial process discharges which cannot be subjected to electrochemical oxidation due to their tendency to polymerise at the anode, forming compact, adhering, and non-conductive films rapidly deactivating their functions. The most common example of species unsuitable for anodic electro-oxidation treatments are organic molecules presenting conjugated or aromatic unsaturated bonds, whose reactivity with respect to polymerisation is notoriously increased by the concurrent presence of electron-withdrawing substituents, which may act as leaving groups in nucleophilic substitution reactions, starting a process of chain polymerisation with other molecules of the same species. Chlorinated derivatives on the ring of benzoic acid or of trifluorobenzene are just one of the most typical examples of substances present in industrial wastes for which no appropriate abatement strategy exists at present, and that subjected to electro-oxidation form pitch which may deactivate industrially used anodes. Such compounds may be utilised either per se, or as an intermediate of synthesis of highly fluorinated aromatic compounds in the pharmaceutical industry, in the formulation of herbicides and dyes, in the synthesis of chelating polymers or in manufacturing of liquid crystals.
Another field in which it is necessary to identify efficient and cheap processes of organic species abatement is the reclamation of aquifer layers from polluting species derived from agricultural treatments, herbicides in particular. For example, the systemic herbicides of the family of picolinic acid derivatives (such as picloram, or 4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) have a tendency to a poor adhesion to the soil and to be leached until reaching the aquifer layers. Also for the abatement of this kind of molecule, both as an industrial exhaust of the relevant synthesis process and as a contaminant of water, it is necessary to identify an effective and cheap treatment, since for the time being there does not exist any suitable alternative, either of chemical or of electrochemical type, to incineration.